550 research outputs found
Effectiveness of a multi-level intervention to improve tobacco policy in alcohol addiction treatment centers
No full textMeasurement of Collins asymmetries in inclusive production of charged pion pairs in e+e− annihilation at BABAR
No full textWe present measurements of Collins asymmetries in the inclusive process e+e−→ππX, where π stands for charged pions, at a center-of-mass energy of 10.6 GeV. We use a data sample of 468 fb−1 collected by the BABAR experiment at the PEP-II B factory at SLAC, and consider pairs of charged pions produced in opposite hemispheres of hadronic events. We observe clear asymmetries in the distributions of the azimuthal angles in two distinct reference frames. We study the dependence of the asymmetry on several kinematic variables, finding that it increases with increasing pion momentum and momentum transverse to the analysis axis, and with increasing angle between the thrust and beam axis
Dalitz plot analyses of B-0 -> (D-DK+)-K-0 and B+-> (D)over-bar(-)D(0)K(+) decays
No full text© 2015, APS Journal
High throughput particle analysis: combining dielectrophoretic particle focussing with confocal optical detection
No full textA microflow cytometer has been fabricated that detects and counts fluorescent particles flowing through a microchannel at a high speed based upon their fluorescence emission intensity. Dielectrophoresis is used to continuously focus particles within the flowing fluid stream into the centre of the device, which is 40 μm high and 250 μm wide. The method ensures that all the particles pass through an interrogation region approximately 5 μm in diameter, which is created by focusing a beam of light into a spot. The functioning of the device was demonstrated by detecting and counting fluorescent latex particles at a rate of up to 250 particles/s. A mixture of three different populations of latex particle was used, each sub-population with a distinct level of fluorescent intensity. The device was evaluated by comparison with a conventional fluorescent activated cell sorter (FACS) and numerical simulation demonstrated that for 6 mico m beads, and for this design of chip the theoretical throughput is of the order of 1000 particles/s (corresponding to a particle velocty of 1 mm/s)
Numerical modeling of dielectrophoretic effect for manipulation of bio-particles
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This text describes different aspects of the design of a Doctor-on-a-Chip device. Doctor-on-a-Chip is a DNA analysis system integrated on a single chip, which should provide all of the advantages that stem from the system integration, such as small sample volume, fast and accurate analysis, and low cost. The text describes all of the steps of the on-chip sample analysis, including DNA extraction from the sample, purification, PCR amplification, novel dielectrophoretic sorting of the DNA molecules, and finally detection.
The overview is given of the technologies which are available to make the integration on a single chip possible. The microfluidic technologies that are used to manipulate the sample and other chemical reagents are already known and in this text they are analyzed in terms of their feasibility in the on-chip system integration. These microfluidic technologies include, but are not limited to, microvalves, micromixers, micropumps, and chambers for PCR amplification.
The novelty in the DNA analysis brought by Doctor-on-a-Chip is the way in which the different DNA molecules in the sample (for example, human and virus DNA) are sorted into different populations. This is done by means of dielectrophoresis – the force experienced by dielectric particles (such as DNA molecules) when subject to a non-uniform electric field. Different DNA molecules within a sample experience different dielectrophoretic forces within the same electric field, which makes their separation, and therefore detection, possible.
In this text, the emphasis is put on numerical modelling of the dielectrophoretic effect on biological particles. The importance of numerical modelling lies in the fact that with the accurate model it is easier to design systems of microelectrodes for dielectrophoretic separation, and tune their sub-micrometre features to achieve the maximum separation efficacy. The numerical model described in this text is also experimentally verified with the novel microelectrodes design for dielectrophoretic separation, which is successfully used to separate the mixture of different particles in the micron and sub-micron range
Novel Methods to Access Bioactive Molecules
No full textThis thesis is divided into two chapters detailing research on applying microwave methodology to access aminated nucleosides in significantly reduced time frames, and applying the Belluš-Claisen reaction to produce non-proteogenic dipeptides.
1. Amination of Nucleosides Using Microwave Methodology
2,2’-Anhydrouridine undergoes a ring opening reaction with aliphatic amines to give the corresponding aminated product. Under conventional heating reaction times are extremely lengthy, taking at least 3 to 4 days and up to a month in the case of very hindered amines. A modified procedure using microwave irradiation has proven to drastically reduce reaction time and has allowed access to novel nucleosides on gram scale.
2. Functionalised Amino Acids via the Belluš-Claisen Rearrangement
The Belluš-Claisen reaction is a [3,3] sigmatropic rearrangement of allylic amines, ethers and thioethers to give the corresponding amide, ester of thioester. A modified procedure of the Belluš-Claisen rearrangement was used to prepare functionalised dipeptides by reaction of a ketene prepared from N-phthaloylglycyl chloride in situ with allylic amino acid derivatives in the presence of a Lewis Acid and diisopropylethylamine. Rearrangments were successfully carried out using N,N-diallyl alanine and N-allyl proline. A range of N-allyl proline derivatives are demonstrated. However, attempts to repeat the reaction with structurally more complex amino acids did not result in successful reactions
Estudo da influência das ligações de hidrogênio intramoleculares no rearranjo de claisen
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Programa de Pós-Graduação em Química.O uso de pesticidas na agricultura aumenta o rendimento e a qualidade dos produtos, reduzindo o trabalho e os gastos com energia. Porém o uso intenso de diversos pesticidas, principalmente herbicidas, fungicidas e inseticidas, que são aplicados diretamente na lamina d'água, em plantação de arroz, por exemplo, e dependendo das condições pluviométricas e de manejo podem ser carreados para fora da lavoura afetando o sistema aquático e o solo. A enzima Corismato mutase está ausente no metabolismo de mamíferos e, por esta razão, se torna um alvo na produção de inibidores com finalidade pesticida não nociva à saúde humana, justificando assim o interesse no estudo de seu mecanismo de ação. Esta reação é formalmente o rearranjo de Claisen que não tem seu mecanismo completamente desvendado. Estudos preliminares realizados com o composto 4-(aliloxi)benzofuran-3-il) carboximetil ester em meio ácido e básico mostraram que o composto se rearranja somente em meio ácido, sugerindo a possibilidade da ligação ser catalisado por uma ligação de hidrogênio intramolecular. Novos compostos derivados do ácido salicílico foram sintetizados com intuito de estudar o efeito das ligações de hidrogênio. As determinações dos pKas e dos perfis de pH destes composto sugerem que a reação pode estar sendo catalisada por ligações de hidrogênio intramoleculares
Arthroscopy or ultrasound in undergraduate anatomy education: a randomized cross-over controlled trial
No full textBackground: The exponential growth of image-based diagnostic and minimally invasive interventions requires a detailed three-dimensional anatomical knowledge and increases the demand towards the undergraduate anatomical curriculum. This randomized controlled trial investigates whether musculoskeletal ultrasound (MSUS) or arthroscopic methods can increase the anatomical knowledge uptake.
Methods: Second-year medical students were randomly allocated to three groups. In addition to the compulsory dissection course, the ultrasound group (MSUS) was taught by eight, didactically and professionally trained, experienced student-teachers and the arthroscopy group (ASK) was taught by eight experienced physicians. The control group (CON) acquired the anatomical knowledge only via the dissection course. Exposure (MSUS and ASK) took place in two separate lessons (75 minutes each, shoulder and knee joint) and introduced standard scan planes using a 10-MHz ultrasound system as well as arthroscopy tutorials at a simulator combined with video tutorials. The theoretical anatomic learning outcomes were tested using a multiple-choice questionnaire (MCQ), and after cross-over an objective structured clinical examination (OSCE). Differences in student's perceptions were evaluated using Likert scale-based items.
Results: The ASK-group (n = 70, age 23.4 (20--36) yrs.) performed moderately better in the anatomical MC exam in comparison to the MSUS-group (n = 84, age 24.2 (20--53) yrs.) and the CON-group (n = 88, 22.8 (20--33) yrs.; p = 0.019). After an additional arthroscopy teaching 1 % of students failed the MC exam, in contrast to 10 % in the MSUS- or CON-group, respectively. The benefit of the ASK module was limited to the shoulder area (p < 0.001). The final examination (OSCE) showed no significant differences between any of the groups with good overall performances. In the evaluation, the students certified the arthroscopic tutorial a greater advantage concerning anatomical skills with higher spatial imagination in comparison to the ultrasound tutorial (p = 0.002; p < 0.001).
Conclusions: The additional implementation of arthroscopy tutorials to the dissection course during the undergraduate anatomy training is profitable and attractive to students with respect to complex joint anatomy. Simultaneous teaching of basic-skills in musculoskeletal ultrasound should be performed by medical experts, but seems to be inferior to the arthroscopic 2D-3D-transformation, and is regarded by students as more difficult to learn. Although arthroscopy and ultrasound teaching do not have a major effect on learning joint anatomy, they have the potency to raise the interest in surgery
Kinematic Distributions and Nuclear Effects of Production in 920 GeV Fixed-Target Proton-Nucleus Collisions
No full textMeasurements of the kinematic distributions of mesons produced in C, Ti and W collisions at in the Feynman- region -0.34 < x_{F} < 0.14 and for transverse momentum up to are presented. The and dependencies of the nuclear suppression parameter, , are also given. The results are based on mesons in both the and decay channels. The data have been collected by the HERA-B experiment at the HERA proton ring of the DESY laboratory. The measurement explores the negative region of for the first time. The average value of in the measured region is . The data suggest that the strong nuclear suppression of production previously observed at high turns into an enhancement at negative
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